“Any opt-out system that relies upon presumed consent is impractical, ambiguous and may be unethical,” he said. “Everything should be done, instead, to promote organ donation through explicit and informed consent.”

“It is indisputable that the introduction of an opt-out system will result in more organs being available for transplant,” she said. “We already know that the majority of people in Scotland have not registered as organ donors, despite research showing that up to 90 percent of people across the country support a system of presumed consent.”

The organization pointed to a children’s hospital in the 1990s at which body parts “were retained without consultation and with the presumed consent of parents.”

Mata noted such programs already are in place in Wales and Spain.

But he described what he called a “pivotal flaw.”

“It does not draw the line between presumed consent and explicit consent,” he noted.

“It is crucial that organs or issues should only be removed if prior consent has been given,” he said. “Any system where body parts of removed without assured consent would be considered ethically unacceptable.”

He noted even McTaggart admitted there is “a risk the family may make a false statement about their knowledge of the deceased person’s wishes in order to give expression to their own view.”

Using tissue and organs after consent is the only solution, he said.

“Any other system has the potential to undermine the concept of organ donation as a gift, erode trust in the [National Health Service] and to negatively impact on donation numbers.”

He noted a government report already has recommended that the way to increase organ donor registry participation could happen “at a relatively modest cost through a more extensive publicity and engagement program, perhaps akin to that of blood donation.”